Floating DC/DC Converter Chassis Potential Control in EVs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electric vehicles with rubber tires face safety hazards due to high grounding resistance, leading to potential hazardous voltage differences between the chassis and ground in case of insulation faults, which existing solutions like grounded lines or double insulation increase complexity and cost.
Innovation Solution
An electrically floating functional unit with a voltage reference point and a safety unit that actively matches the electric potential to a target value, triggering an insulation fault event if mismatch occurs, using a symmetrical DC/DC-converter and safety unit to quickly disconnect voltage supplies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a grounded line is added to the overhead lines, then safety against hazardous voltages is improved, but device complexity and installation costs increase
Solution Approach 1:
The patent introduces an intermediary device (grounding device with voltage sensor and control circuit) between the overhead line system and the vehicle chassis, which actively monitors and controls the chassis potential without requiring modification of the overhead line infrastructure. This mediator approach maintains safety while avoiding the complexity of adding grounded lines to the overhead system.
Solution Approach 2:
The system dynamically changes the electrical parameter (chassis potential) by actively controlling the grounding connection based on detected voltage conditions. The control circuit adjusts the grounding state in real-time, transitioning the chassis from an isolated state to a grounded state when hazardous voltages are detected, thereby maintaining safety without permanent structural modifications.
2Reliability
If double insulation is introduced around parts connected to overhead lines, then safety is improved, but device complexity, costs, vehicle weight and installation space requirements increase
Solution Approach 1:
The patent extracts the safety function from the vehicle structure (insulation layers) and relocates it to an independent electrical control system. By removing the need for physical insulation barriers and implementing active electrical control, the vehicle weight is reduced while maintaining equivalent or superior safety performance through intelligent monitoring and control.
Solution Approach 2:
The patent replaces the mechanical/physical insulation system (double insulation layers) with an electrical control system (voltage sensor, control circuit, and switching device). This substitution eliminates the need for heavy insulating materials and complex structural modifications, reducing vehicle weight and installation space while providing more flexible and responsive safety control.
3Device complexity
If the functional unit is electrically floating, then insulation requirements are reduced, but risk of hazardous voltage between chassis and ground increases
Solution Approach 1:
The patent implements a feedback control mechanism where the voltage sensor continuously monitors the chassis potential relative to ground, and the control circuit adjusts the grounding connection based on the detected voltage level. This closed-loop feedback system allows the functional unit to operate in a floating state under normal conditions (reducing insulation requirements) while automatically providing grounding protection when hazardous voltages are detected, thereby resolving the contradiction between operational simplicity and safety.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Electric vehicle system (10) comprising: - a functional unit (11) configured to provide at least one electrical function, in particular a DC/DC-converter (16), the functional unit (11) being electrically floating and having at least one voltage reference point (13); and - a safety unit (34) configured for actively matching an electric potential (Vr) at the voltage reference point (13) to a target value (V0), the safety unit (34) being configured to trigger an insulation fault event if the matching is impossible.